Development of a quality of life workpackage for the monalisa trial to evaluate the impact of serial liquid biopsies: lessons learned designing the monalisa trial

approach.CfDNA was isolated from PB and BM plasma and analyzed with digital droplet (dd)PCR for gene amplifications and ALK hotspot mutations or sequenced after preparation of NGS custom capture libraries for 142 whole coding genes and selected SNVs and indels.Results: In our cohort the marker trio (PB cfDNA, BM cfDNA, BM DTC) correlated in 63% (96/153) of all analyzed TPs.In 32 samples only PB or BM cfDNA was positive and for 17 samples MRD was exclusively detected by DTC analysis highlighting the added value of this cellbased approach.In 82% of events at least one of the markers was positive, mostly in PB cfDNA, remarkably between 7 days and 17 weeks prior clinical confirmation of the relapse.GD2 was detected in all BM DTC positive samples.Conclusion: Multi-modal analysis of genetic markers in PB and BM plasma cfDNA in combination with AIPF-based DTC enumeration is a highly sensitive approach for disease monitoring and for assessing immunotherapy targets like GD2.These combined liquid biopsy IVDRcompliant tests will be an important component of neuroblastoma diagnostics and tested in a prospective pragmatical clinical trial.